Silane mixtures and process for preparing same

ABSTRACT

The invention relates to silane mixtures comprising a silane of the formula I
 
(R 1 ) y (R 2 ) 3-y Si—R 3 —(S—R 4 ) n —S x —R 5   (I)
 
and a silane of the formula II
 
(R 1 ) y (R 2 ) 3-y Si—R 3 —S—R 4 —S—R 3 —Si(R 1 ) y (R 2 ) 3-y   (II)
 
where the molar ratio of silane of the formula I to silane of the formula II is 15:85-90:10.
 
     The silane mixture according to the invention can be prepared by mixing the silanes of the formula I and silanes of the formula II.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is the national stage of international application PCT/EP2018/081486, filed on Nov. 16, 2018, and claims the benefit of the filing date of German Appl. No. 10 2017 221 269.1, filed on Nov. 28, 2017.

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Inventions described in the present application were developed within the scope of a joint research agreement between the applicant and Continental Reifen Deutschland GmbH.

The invention relates to silane mixtures and to processes for preparation thereof.

EP 0670347 and EP 0753549 disclose rubber mixtures comprising at least one crosslinker, a filler, optionally further rubber auxiliaries and at least one reinforcing additive of the formula R¹R²R³Si—X¹—(—S_(x)—Y—)_(m)—(—S_(x)—X²—SiR¹R²R³)_(n).

JP2012149189 discloses the silane of the formula (R¹O)_(l)R² _((3-l))Si—R³—(S_(m)R⁴)_(n)—S—R⁵ with R⁵=—C(═O)—R⁶

R⁶=C1-C20.

In addition, EP 1375504 discloses silanes of the formula (R¹O)_((3-p))(R²)_(p)Si—R³—S_(m)—R⁴—(S_(n)—R⁴)_(q)—S_(m)—R³—Si(R²)_(p)(OR¹)_((3-p)).

WO 2005/059022 discloses rubber mixtures comprising a silane of the formula [R²R³R⁴Si—R⁵—S—R⁶—R⁷—]R¹.

Additionally known are rubber mixtures comprising a bifunctional silane and a further silane of the formula (Y)G(Z) (WO 2012/092062) and rubber mixtures comprising bistriethoxysilylpropyl polysulfide and bistriethoxysilylpropyl monosulfide (EP1085045).

EP 1928949 discloses a rubber mixture comprising the silanes (H₅C₂O)₃Si—(CH₂)₃—X—(CH₂)₆—S₂—(CH₂)₆—X—(CH₂)₃—Si(OC₂H₅)₃ and/or (H₅C₂O)₃Si—(CH₂)₃—X—(CH₂)₁₀—S₂—(CH₂)₆—X—(CH₂)₁₀—Si(OC₂H₅)₃ and (H₅C₂O)₃Si—(CH₂)₃—S_(m)—(CH₂)₃—Si(OC₂H₅)₃.

It is an object of the present invention to provide silane mixtures having improved rolling resistance and improved fracture energy density in rubber mixtures compared to silanes known from the prior art.

The invention provides a silane mixture comprising a silane of the formula I (R¹)_(y)(R²)_(3-y)Si—R³—(S—R⁴)_(n)—S_(x)—R⁵  (I) and a silane of the formula II (R¹)_(y)(R²)_(3-y)Si—R³—S—R⁴—S—R³—Si(R¹)_(y)(R²)_(3-y)  (II)

where R¹ are the same or different and are C1-C10-alkoxy groups, preferably methoxy or ethoxy groups, phenoxy group, C4-C10-cycloalkoxy groups or alkyl polyether group O—(R⁶—O)_(r)—R⁷ where R⁶ are the same or different and are a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-C30 hydrocarbon group, preferably —CH₂—CH₂—, r is an integer from 1 to 30, preferably 3 to 10, and R⁷ is unsubstituted or substituted, branched or unbranched monovalent alkyl, alkenyl, aryl or aralkyl groups, preferably a C₁₃H₂₇-alkyl group,

R² is the same or different and is C6-C20-aryl groups, preferably phenyl, C1-C10-alkyl groups, preferably methyl or ethyl, C2-C20-alkenyl group, C7-C20-aralkyl group or halogen, preferably Cl,

R³ are the same or different and are a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-C30 hydrocarbon group, preferably C1-C20, more preferably C1-C10, even more preferably C2-C8, especially preferably CH₂CH₂ and CH₂CH₂CH₂,

R⁴ are the same or different and are a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-C30 hydrocarbon group, preferably C1-C20, more preferably C1-C10, even more preferably C2-C7, especially preferably (CH₂)₆,

x is an integer from 1 to 10, preferably 1 to 4, more preferably 1 or 2,

when x is 1 R⁵ is hydrogen or a —C(═O)—R⁸ group with R⁸=hydrogen, a C1-C20 alkyl group, preferably C1-C17, C6-C20-aryl groups, preferably phenyl, C2-C20-alkenyl group or a C7-C20-aralkyl group and n is 0, 1, 2 or 3, preferably 1,

when x is 2 to 10 R⁵ is —(R⁴—S)_(n)—R³—Si(R¹)_(y)(R²)_(3-y) and n is 1, 2 or 3, preferably 1, and y are the same or different and are 1, 2 or 3,

and the molar ratio of silane of the formula I to silane of the formula II is 20:80-90:10, preferably 25:75-90:10, more preferably 30:70-90:10, most preferably 35:65-90:10.

Preferably, the silane mixture may comprise a silane of the formula I (R¹)_(y)(R²)_(3-y)Si—R³—(S—R⁴)_(n)—S_(x)—R⁵  (I) and a silane of the formula II (R¹)_(y)(R²)_(3-y)Si—R³—S—R⁴—S—R³—Si(R¹)_(y)(R²)_(3-y)  (II)

where n is 1 and R¹, R², R³, R⁴, R⁵, x and y have the same definition as described above.

The silane mixture according to the invention may comprise further additives or consist solely of silanes of the formula I and silanes of the formula II.

The silane mixture according to the invention may comprise oligomers that form as a result of hydrolysis and condensation of the silanes of the formula I and/or silanes of the formula II.

The silane mixture according to the invention may have been applied to a support, for example wax, polymer or carbon black. The silane mixture according to the invention may have been applied to a silica, in which case the binding may be physical or chemical.

R³ and R⁴ may independently be —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂—, —CH(CH₃)—, —CH₂CH(CH₃)—, —CH(CH₃)CH₂—, —C(CH₃)₂—, —CH(C₂H₅)—, —CH₂CH₂CH(CH₃)—, —CH(CH₃)CH₂CH₂—, —CH₂CH(CH₃)CH₂—, —CH₂CH₂CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—,—CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂— or

R¹ may preferably be methoxy or ethoxy.

Silanes of the formula I may preferably be:

(EtO)₃Si—CH₂—S₂—CH₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₂—S₂—(CH₂)₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₃—S₂—(CH₂)₃—Si(OEt)₃,

(EtO)₃Si—CH₂—S₄—CH₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₂—S₄—(CH₂)₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₃—S₄—(CH₂)₃—Si(OEt)₃,

(EtO)₃Si—CH₂—S—(CH₂)—S₂—(CH₂)—S—CH₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₂—S—(CH₂)—S₂—(CH₂)—S—(CH₂)₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)—S₂—(CH₂)—S—(CH₂)₃—Si(OEt)₃,

(EtO)₃Si—CH₂—S—(CH₂)₂—S₂—(CH₂)₂—S—CH₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₂—S—(CH₂)₂—S₂—(CH₂)₂—S—(CH₂)₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₂—S₂—(CH₂)₂—S—(CH₂)₃—Si(OEt)₃,

(EtO)₃Si—CH₂—S—(CH₂)₃—S₂—(CH₂)₃—S—CH₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₂—S—(CH₂)₃—S₂—(CH₂)₃—S—(CH₂)₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃—S₂—(CH₂)₃—S—(CH₂)₃—Si(OEt)₃,

(EtO)₃Si—CH₂—S—(CH₂)₄—S₂—(CH₂)₄—S—CH₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₂—S—(CH₂)₄—S₂—(CH₂)₄—S—(CH₂)₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₄—S₂—(CH₂)₄—S—(CH₂)₃—Si(OEt)₃,

(EtO)₃Si—CH₂—S—(CH₂)₅—S₂—(CH₂)₅—S—CH₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₂—S—(CH₂)₅—S₂—(CH₂)₅—S—(CH₂)₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₅—S₂—(CH₂)₅—S—(CH₂)₃—Si(OEt)₃,

(EtO)₃Si—CH₂—S—(CH₂)₆—S₂—(CH₂)₆—S—CH₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₂—S—(CH₂)₆—S₂—(CH₂)₆—S—(CH₂)₂—Si(OEt)₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S₂—(CH₂)₆—S—(CH₂)₃—Si(OEt)₃.

(EtO)₃Si—(CH₂)₃—S_C(═O)—CH₃,

(EtO)₃Si—(CH₂)₃—S_C(═O)—C₂H₅,

(EtO)₃Si—(CH₂)₃—S_C(═O)—C₃H₇,

(EtO)₃Si—(CH₂)₃—S—C(═O)—C₄H₅,

(EtO)₃Si—(CH₂)₃—S—C(═O)—C₅H₁₁,

(EtO)₃Si—(CH₂)₃—S_C(═O)—C₆H₁₃,

(EtO)₃Si—(CH₂)₃—S_C(═O)—C₇H₁₅,

(EtO)₃Si—(CH₂)₃—S_C(═O)—C₉H₁₉,

(EtO)₃Si—(CH₂)₃—S_C(═O)—C₁₁H₂₃,

(EtO)₃Si—(CH₂)₃—S_C(═O)—C₁₃H₂₇,

(EtO)₃Si—(CH₂)₃—S_C(═O)—C₁₅H₃₁,

(EtO)₃Si—(CH₂)₃—S_C(═O)—C₁₇H₃₅,

(EtO)₃Si—(CH₂)₃—S—(CH₂)—S_C(═O)—CH₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)—S_C(═O)—C₂H₅,

(EtO)₃Si—(CH₂)₃—S—(CH₂)—S_C(═O)—C₃H₇,

(EtO)₃Si—(CH₂)₃—S—(CH₂)—S_C(═O)—C₄H₉,

(EtO)₃Si—(CH₂)₃—S—(CH₂)—S_C(═O)—C₅H₁₁,

(EtO)₃Si—(CH₂)₃—S—(CH₂)—S_C(═O)—C₆H₁₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)—S_C(═O)—C₇H₁₅,

(EtO)₃Si—(CH₂)₃—S—(CH₂)—S_C(═O)—C₉H₁₉,

(EtO)₃Si—(CH₂)₃—S—(CH₂)—S_C(═O)—C₁₁H₂₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)—S_C(═O)—C₁₃H₂₇,

(EtO)₃Si—(CH₂)₃—S—(CH₂)—S_C(═O)—C₁₅H₃₁,

(EtO)₃Si—(CH₂)₃—S—(CH₂)—S_C(═O)—C₁₇H₃₅,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₂—S_C(═O)—CH₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₂—S_C(═O)—C₂H₅,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₂—S_C(═O)—C₃H₇,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₂—S_C(═O)—C₄H₉,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₂—S_C(═O)—C₅H₁₁,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₂—S_C(═O)—C₆H₁₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₂—S_C(═O)—C₇—H₁₅,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₂—S_C(═O)—C₉H₁₉,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₂—S_C(═O)—C₁₁H₂₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₂—S_C(═O)—C₁₃H₂₇,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₂—S_C(═O)—C₁₅H₃₁,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₂—S_C(═O)—C₁₇H₃₅,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃—S_C(═O)—CH₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃—S_C(═O)—C₂H₅,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃—S_C(═O)—C₃H₇,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃— S_C(═O)—C₄H₉,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃— S_C(═O)—C₅H₁₁,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃— S_C(═O)—C₆H₁₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃— S_C(═O)—C₇H₁₅,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃— S_C(═O)—C₉H₁₉,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃—S_C(═O)—C₁₁H₂₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃—S_C(═O)—C₁₃H₂₇,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃—S_C(═O)—C₁₅H₃₁,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃—S_C(═O)—C₁₇H₃₅,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S_C(═O)—CH₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S_C(═O)—C₂H₅,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S_C(═O)—C₃H₇,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S_C(═O)—C₄H₉,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S_C(═O)—C₅H₁₁,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S_C(═O)—C₆H₁₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S_C(═O)—C₇H₁₅,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S_C(═O)—C₉H₁₉,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S_C(═O)—C₁₁H₂₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S_C(═O)—C₁₃H₂₇,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S_C(═O)—C₁₅H₃₁,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S_C(═O)—C₁₇H₃₅,

Especially preferred is the silane of the formula I

(EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S₂—(CH₂)₆—S—(CH₂)₃—Si(OEt)₃, (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—CH₃, (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—C₇H₁₅ and (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—C₁₇H₃₅.

Silanes of the formula II may preferably be:

(EtO)₃Si—(CH₂)—S—(CH₂)—Si(OEt)₃,

(EtO)₃Si—(CH₂)₂—S—(CH₂)₂Si(OEt)₃,

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃Si(OEt)₃,

(EtO)₃Si—(CH₂)₄—S—(CH₂)₄Si(OEt)₃,

(EtO)₃Si—(CH₂)₅—S—(CH₂)₅Si(OEt)₃,

(EtO)₃Si—(CH₂)₆—S—(CH₂)₆Si(OEt)₃,

(EtO)₃Si—(CH₂)₇—S—(CH₂)₇Si(OEt)₃,

(EtO)₃Si—(CH₂)₈—S—(CH₂)₈Si(OEt)₃,

(EtO)₃Si—(CH₂)₉—S—(CH₂)₉Si(OEt)₃,

(EtO)₃Si—(CH₂)₁₉—S—(CH₂)₁₀Si(OEt)₃,

Especially preferred is the silane of the formula II

(EtO)₃Si—(CH₂)₃—S—(CH₂)₃Si(OEt)₃.

Very particular preference is given to a silane mixture of (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S₂—(CH₂)₆—S—(CH₂)₃—Si(OEt)₃, (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—CH₃, (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—C₇H₁₅ or (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—C₁₇H₃₅ and (EtO)₃Si—(CH₂)₃—S—(CH₂)₃Si(OEt)₃.

The present invention further provides a process for preparing the silane mixture according to the invention, which is characterized in that the silane of the formula I (R¹)_(y)(R²)_(3-y)Si—R³—(S—R⁴)_(n)—S_(x)—R⁵  (I) and a silane of the formula II (R¹)_(y)(R²)_(3-y)Si—R³—S—R⁴—S—R³—Si(R¹)_(y)(R²)_(3-y)  (II)

where R¹, R², R³, R⁴, R⁵, n, x and y have the definition given above

are mixed in a molar ratio of 20:80-90:10, preferably 25:75-90:10, more preferably 30:70-90:10, most preferably 35:65-90:10.

Preferably, a silane of the formula I (R¹)_(y)(R²)_(3-y)Si—R³—(S—R⁴)_(n)—S_(x)—R⁵  (I) and a silane of the formula II (R¹)_(y)(R²)_(3-y)Si—R³—S—R⁴—S—R³—Si(R¹)_(y)(R²)_(3-y)  (II)

where R¹, R², R³, R⁴, R⁵, x and y have the definition given above and n is 1 can be mixed.

The process according to the invention can be conducted with exclusion of air. The process according to the invention can be conducted under protective gas atmosphere, for example under argon or nitrogen, preferably under nitrogen.

The process according to the invention can be conducted at standard pressure, elevated pressure or reduced pressure. Preferably, the process according to the invention can be conducted at standard pressure.

Elevated pressure may be a pressure of 1.1 bar to 100 bar, preferably of 1.1 bar to 50 bar, more preferably of 1.1 bar to 10 bar and very preferably of 1.1 to 5 bar.

Reduced pressure may be a pressure of 1 mbar to 1000 mbar, preferably 250 mbar to 1000 mbar, more preferably 500 mbar to 1000 mbar.

The process according to the invention can be conducted between 20° C. and 100° C., preferably between 20° C. and 50° C., more preferably between 20° C. and 30° C.

The process according to the invention can be conducted in a solvent, for example methanol, ethanol, propanol, butanol, cyclohexanol, N,N-dimethylformamide, dimethyl sulfoxide, pentane, hexane, cyclohexane, heptane, octane, decane, toluene, xylene, acetone, acetonitrile, carbon tetrachloride, chloroform, dichloromethane, 1,2-dichloroethane, tetrachloroethylene, diethyl ether, methyl tert-butyl ether, methyl ethyl ketone, tetrahydrofuran, dioxane, pyridine or methyl acetate, or a mixture of the aforementioned solvents. The process according to the invention can preferably be conducted without solvent.

The silane mixture according to the invention can be used as adhesion promoter between inorganic materials, for example glass beads, glass flakes, glass surfaces, glass fibres, or oxidic fillers,

preferably silicas such as precipitated silicas and fumed silicas,

and organic polymers, for example thermosets, thermoplastics or elastomers, or as crosslinking agents and surface modifiers for oxidic surfaces.

The silane mixture according to the invention can be used as coupling reagents in filled rubber mixtures, examples being tyre treads, industrial rubber articles or footwear soles.

Advantages of the silane mixtures according to the invention are improved rolling resistance and improved reinforcement in rubber mixtures.

EXAMPLES

NMR method: The molar ratios and proportions by mass reported as analysis results in the examples come from ¹³C NMR measurements with the following indices: 100.6 MHz, 1000 scans, solvent: CDCl₃, internal standard for calibration: tetramethylsilane, relaxation aid: Cr(acac)₃; for the determination of the proportion by mass in the product, a defined amount of dimethyl sulfone is added as internal standard and the molar ratios of the products are used to calculate the proportion by mass.

Comparative Example 1: 3-octanoylthio-1-propyltriethoxysilane, NXT Silane from Momentive Performance Materials.

Comparative Example 2: bistriethoxysilyloctane from ABCR GmbH.

Comparative Example 3: bis(triethoxysilylpropyl) disulfide from Evonik Industries AG.

Comparative Example 4: 1-chloro-6-thiopropyltriethoxysilylhexane NaOEt (21% in EtOH; 1562 g; 4.820 mol) was metered into mercaptopropyltriethoxysilane (1233 g; 5.170 mol) over the course of 1 h while stirring at room temperature. On completion of addition, the reaction mixture was heated at reflux for 2 h and then left to cool to room temperature. The intermediate formed was metered into 1,6-dichlorohexane (4828 g; 31.14 mol) that had been heated to 80° C. over the course of 30 min. On completion of addition, the reaction mixture was heated at reflux for 3 h, before being left to cool to room temperature. The reaction mixture was filtered and the filtercake was rinsed with EtOH. The volatile constituents were removed under reduced pressure and the 1-chloro-6-thiopropyltriethoxysilylhexane intermediate (yield: 89%, molar ratio: 97% 1-chloro-6-thiopropyltriethoxysilylhexane, 3% bis(thiopropyltriethoxysilyl)hexane; % by weight: 95% by weight of 1-chloro-6-thiopropyltriethoxysilylhexane, 5% by weight of 1,6-bis(thiopropyltriethoxysilyl)hexane) was obtained as a colourless to brown liquid.

Comparative Example 5: 6-bis(thiopropyltriethoxysilylhexyl) disulfide

6-Bis(thiopropyltriethoxysilylhexyl) disulfide was prepared according to Synthesis Example 1 and

Example 1 of EP 1375504.

By contrast with Synthesis Example 1 of EP1375504, the intermediate was not distilled.

Analysis: (88% yield, molar ratio: silane of the formula I: 94%

(EtO)₃Si(CH₂)₃S(CH₂)₆S₂(CH₂)₆S(CH₂)₃Si(OEt)₃ and silane of the formula II: 6%

(EtO)₃Si(CH₂)₃S(CH₂)₆S(CH₂)₃Si(OEt)₃, % by weight: silane of the formula I: 95% by weight of

(EtO)₃Si(CH₂)₃S(CH₂)₆S₂(CH₂)₆S(CH₂)₃Si(OEt)₃ and silane of the formula II: 5% by weight of

(EtO)₃Si(CH₂)₃S(CH₂)₆S(CH₂)₃Si(OEt)₃)

Comparative Example 6: S-(6-((3-(triethoxysilyl)propyl)thio)hexyl) thioacetate Na₂CO₃ (59.78 g; 0.564 mol) and an aqueous solution of NaSH (40% in water; 79.04 g; 0.564 mol) were initially charged together with water (97.52 g). Then tetrabutylphosphonium bromide (TBPB) (50% in water; 3.190 g; 0.005 mol) was added and acetyl chloride (40.58 g; 0.517 mol) was added dropwise over the course of 1 h, during which the reaction temperature was kept at 25-32° C. On completion of addition of the acetyl chloride, the mixture was stirred at room temperature for 1 h. Then TBPB (50% in water; 3.190 g; 0.005 mol) and 1-chloro-6-thiopropyltriethoxysilylhexane (from Comparative Example 4; 167.8 g; 0.470 mol) were added and the mixture was heated at reflux for 3-5 h. The progress of the reaction was monitored by means of gas chromatography. Once the 1-chloro-6-thiopropyltriethoxysilylhexane had reacted to an extent of >96%, water was added until all the salts had dissolved and the phases were separated. The volatile constituents of the organic phase were removed under reduced pressure, and S-(6-((3-(triethoxysilyl)propyl)thio)hexyl) thioacetate (yield: 90%, molar ratio: 97% S-(6-((3-(triethoxysilyl)propyl)thio)hexyl) thioacetate, 3% bis(thiopropyltriethoxysilyl)hexane; % by weight: 96% by weight of S-(6-((3-(triethoxysilyl)propyl)thio)hexyl) thioacetate, 4% by weight of 1,6-bis(thiopropyltriethoxysilyl)hexane) was obtained as a yellow to brown liquid.

Comparative Example 7: S-(6-((3-(triethoxysilyl)propyl)thio)hexyl) thiooctanoate Na₂CO₃ (220.2 g; 2.077 mol) and an aqueous solution of NaSH (40% in water; 291.2 g; 2.077 mol) were initially charged together with water (339.2 g). Then tetrabutylammonium bromide (TBAB) (50% in water; 10.96 g; 0.017 mol) was added and octanoyl chloride (307.2 g; 1.889 mol) was added dropwise over the course of 2.5 h, during which the reaction temperature was kept at 24-28° C. On completion of addition of the octanoyl chloride, the mixture was stirred at room temperature for 1 h. Then TBAB (50% in water; 32.88 g; 0.051 mol) and 1-chloro-6-thiopropyltriethoxysilylhexane (from Comparative Example 4, 606.9 g; 1.700 mol) were added and the mixture was heated at reflux for 10 h. Then water was added until all the salts had dissolved and the phases were separated. The volatile constituents of the organic phase were removed under reduced pressure, and S-(6-((3-(triethoxysilyl)propyl)thio)hexyl) thiooctanoate (yield: 95%, molar ratio: 97% S-(6-((3-(triethoxysilyl)propyl)thio)hexyl) thiooctanoate, 3% bis(thiopropyltriethoxysilyl)hexane; % by weight: 96% by weight of S-(6-((3-(triethoxysilyl)propyl)thio)hexyl) thiooctanoate, 4% by weight of 1,6-bis(thiopropyltriethoxysilyl)hexane) was obtained as a yellow to brown liquid.

Comparative Example 8: S-(6((3-(triethoxysilyl)propyl)thio)hexyl) thiooctadecanoate

S-(6-((3-(Triethoxysilyl)propyl)thio)hexyl) thiooctadecanoate was prepared from 1-chloro-6-thiopropyltriethoxysilylhexane (from Comparative Example 4) in accordance with Synthesis Examples 1 and 3 in JP2012149189.

S-(6-((3-(Triethoxysilyl)propyl)thio)hexyl) thiooctadecanoate (yield: 89%, molar ratio: 97% S-(6-((3-(triethoxysilyl)propyl)thio)hexyl) thiooctadecanoate, 3% bis(thiopropyltriethoxysilyl)hexane; % by weight: 97% by weight of S-(6-((3-(triethoxysilyl)propyl)thio)hexyl) thiooctadecanoate, 3% by weight of 1,6-bis(thiopropyltriethoxysilyl)hexane) was obtained as a yellow to brown liquid.

Comparative Example 9: bis(triethoxysilylpropyl) sulfide

To a solution of chloropropyltriethoxysilane (361 g; 1.5 mol; 1.92 eq) in ethanol (360 ml) was added Na₂S (61.5 g; 0.78 mol; 1.00 eq) in portions at such a rate as to not exceed 60° C. Completion of addition was followed by heating at reflux for 3 h, before leaving to cool to room temperature. The reaction product was freed of precipitated salts by filtration. By distillative purification (0.04 mbar; 110° C.), it was possible to obtain the product (yield: 73%, purity: >99% by ¹³C NMR) as a clear liquid.

Comparative Example 10: 6.84 parts by weight of Comparative Example 1 together with 1.65 parts by weight of Comparative Example 2 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 83% (EtO)₃Si(CH₂)₃SCO(CH₂)₆CH₃ and 17% (EtO)₃Si(CH₂)₈Si(OEt)₃.

Comparative Example 11: 6.84 parts by weight of Comparative Example 1 together with 2.47 parts by weight of Comparative Example 2 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 77% (EtO)₃Si(CH₂)₃SCO(CH₂)₆CH₃ and 23% (EtO)₃Si(CH₂)₈Si(OEt)₃.

Comparative Example 12: 6.84 parts by weight of Comparative Example 3 together with 2.65 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 71% (EtO)₃Si(CH₂)₃S₂(CH₂)₃Si(OEt)₃ and 29% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Comparative Example 13: 6.84 parts by weight of Comparative Example 3 together with 3.65 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 64% (EtO)₃Si(CH₂)₃S₂(CH₂)₃Si(OEt)₃ and 36% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Comparative Example 14: 6.30 parts by weight of Comparative Example 1 together with 2.53 parts by weight of Comparative Example 2 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 75% (EtO)₃Si(CH₂)₃SCO(CH₂)₆CH₃ and 25% (EtO)₃Si(CH₂)₈Si(OEt)₃.

Comparative Example 15: 4.20 parts by weight of Comparative Example 1 together with 3.79 parts by weight of Comparative Example 2 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 57% (EtO)₃Si(CH₂)₃SCO(CH₂)₆CH₃ and 43% (EtO)₃Si(CH₂)₈Si(OEt)₃.

Comparative Example 16: 2.10 parts by weight of Comparative Example 1 together with 5.06 parts by weight of Comparative Example 2 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 33% (EtO)₃Si(CH₂)₃SCO(CH₂)₆CH₃ and 67% (EtO)₃Si(CH₂)₈Si(OEt)₃.

Comparative Example 17: 4.10 parts by weight of Comparative Example 3 together with 2.44 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 61% (EtO)₃Si(CH₂)₃S₂(CH₂)₃Si(OEt)₃ and 39% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Comparative Example 18: 2.74 parts by weight of Comparative Example 3 together with 3.65 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 41% (EtO)₃Si(CH₂)₃S₂(CH₂)₃Si(OEt)₃ and 59% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 1: 6.84 parts by weight of Comparative Example 1 together with 1.66 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 83% (EtO)₃Si(CH₂)₃SCO(CH₂)₆CH₃ and 17% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 2: 6.84 parts by weight of Comparative Example 1 together with 2.49 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 77% (EtO)₃Si(CH₂)₃SCO(CH₂)₆CH₃ and 23% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 3 6.84 parts by weight of Comparative Example 5 together with 1.71 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 66% (EtO)₃Si(CH₂)₃S(CH₂)₆S₂(CH₂)₆S(CH₂)₃Si(OEt)₃ and 34% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 4: 6.84 parts by weight of Comparative Example 5 together with 2.57 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 58% (EtO)₃Si(CH₂)₃S(CH₂)₆S₂(CH₂)₆S(CH₂)₃Si(OEt)₃ and 42% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 5: 6.84 parts by weight of Comparative Example 6 together with 1.53 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 80% (EtO)₃Si(CH₂)₃SCOCH₃ and 20% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 6: 6.84 parts by weight of Comparative Example 6 together with 2.29 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 74% (EtO)₃Si(CH₂)₃SCOCH₃ and 26% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 7: 6.84 parts by weight of Comparative Example 7 together with 1.26 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 80% (EtO)₃Si(CH₂)₃SCO(CH₂)₆CH₃ and 20% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 8: 6.84 parts by weight of Comparative Example 7 together with 1.89 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 74% (EtO)₃Si(CH₂)₃SCO(CH₂)₆CH₃ and 26% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 9: 6.84 parts by weight of Comparative Example 8 together with 0.98 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 80% (EtO)₃Si(CH₂)₃SCO(CH₂)₁₆CH₃ and 20% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 10: 6.84 parts by weight of Comparative Example 8 together with 1.46 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 74% (EtO)₃Si(CH₂)₃SCO(CH₂)₁₆CH₃ and 26% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 11: 8.40 parts by weight of Comparative Example 1 together with 1.28 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 89% (EtO)₃Si(CH₂)₃SCO(CH₂)₆CH₃ and 11% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 12: 6.30 parts by weight of Comparative Example 1 together with 2.55 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 75% (EtO)₃Si(CH₂)₃SCO(CH₂)₆CH₃ and 25% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 13: 4.20 parts by weight of Comparative Example 1 together with 3.83 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 57% (EtO)₃Si(CH₂)₃SCO(CH₂)₆CH₃ and 43% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 14: 2.10 parts by weight of Comparative Example 1 together with 5.10 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 33% (EtO)₃Si(CH₂)₃SCO(CH₂)₆CH₃ and 67% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 15: 8.15 parts by weight of Comparative Example 5 together with 1.28 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 74% (EtO)₃Si(CH₂)₃S(CH₂)₆S₂(CH₂)₆S(CH₂)₃Si(OEt)₃ and 26% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 16: 6.11 parts by weight of Comparative Example 5 together with 2.55 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 56% (EtO)₃Si(CH₂)₃S(CH₂)₆S₂(CH₂)₆S(CH₂)₃Si(OEt)₃ and 44% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 17: 4.08 parts by weight of Comparative Example 5 together with 3.83 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 38% (EtO)₃Si(CH₂)₃S(CH₂)₆S₂(CH₂)₆S(CH₂)₃Si(OEt)₃ and 62% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 18: 9.14 parts by weight of Comparative Example 5 together with 1.28 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 76% (EtO)₃Si(CH₂)₃S(CH₂)₆S₂(CH₂)₆S(CH₂)₃Si(OEt)₃ and 24% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 19: 6.86 parts by weight of Comparative Example 5 together with 2.55 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 59% (EtO)₃Si(CH₂)₃S(CH₂)₆S₂(CH₂)₆S(CH₂)₃Si(OEt)₃ and 41% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 20: 4.57 parts by weight of Comparative Example 5 together with 3.83 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 40% (EtO)₃Si(CH₂)₃S(CH₂)₆S₂(CH₂)₆S(CH₂)₃Si(OEt)₃ and 60% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 21: 11.08 parts by weight of Comparative Example 7 together with 1.28 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 85% (EtO)₃Si(CH₂)₃S(CH₂)₆SCO(CH₂)₆CH₃ and 15% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 22: 8.31 parts by weight of Comparative Example 7 together with 2.55 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 72% (EtO)₃Si(CH₂)₃S(CH₂)₆SCO(CH₂)₆CH₃ and 28% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 23: 5.54 parts by weight of Comparative Example 7 together with 3.83 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 55% (EtO)₃Si(CH₂)₃S(CH₂)₆SCO(CH₂)₆CH₃ and 45% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 24: 2.77 parts by weight of Comparative Example 7 together with 5.10 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 32% (EtO)₃Si(CH₂)₃S(CH₂)₆SCO(CH₂)₆CH₃ and 68% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 25: 14.32 parts by weight of Comparative Example 8 together with 1.28 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 85% (EtO)₃Si(CH₂)₃S(CH₂)₆SCO(CH₂)₁₆CH₃ and 15% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 26: 10.74 parts by weight of Comparative Example 8 together with 2.55 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 72% (EtO)₃Si(CH₂)₃S(CH₂)₆SCO(CH₂)₁₆CH₃ and 28% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 27: 7.16 parts by weight of Comparative Example 8 together with 3.83 parts by weight of Comparative Example 9 were weighed into a flat PE bag and mixed. This mixture corresponds to a molar ratio: 55% (EtO)₃Si(CH₂)₃S(CH₂)₆SCO(CH₂)₁₆CH₃ 45% (EtO)₃Si(CH₂)₃S(CH₂)₃Si(OEt)₃.

Example 28: Rubber tests

The formulation used for the rubber mixtures is specified in Table 1 below. The unit phr means parts by weight based on 100 parts of the raw rubber used. The silane mixtures all contain an identical phr amount of silane which reacts with the rubber during the vulcanization. The second silane is added additionally.

TABLE 1 Mixture 5/ Mixture 6/ Mixture 7/ Mixture 8/ Mixture 9 / Mixture 10/ Mixture 11/ Mixture 12/ Mixture 13/ Mixture 14/ Mixture Mixture Mixture Mixture phr phr phr phr phr phr phr phr phr phr 1/phr 2/phr 3/phr 4/phr Inv. Inv. Inv. Inv. Inv. Inv. Inv. Inv. Inv. Inv. 1st stage NR^(a)) 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 BR^(b)) 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 S-SBR^(c)) 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 Silica^(d)) 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 TDAE oil^(e)) 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 6PPD^(f)) 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Antiozonant 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 wax Zinc oxide 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Stearic acid 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Comp. Ex. 10 8.49 Comp. Ex. 11 9.31 Comp. Ex. 12 9.49 Comp. Ex. 13 10.49 Example 1 8.50 Example 2 9.33 Example 3 8.55 Example 4 9.41 Example 5 8.37 Example 6 9.13 Example 7 8.10 Example 8 8.73 Example 9 7.82 Example 10 8.30 2nd stage Stage 1 batch 3rd stage Stage 2 batch DPG^(g)) 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 CBS^(h)) 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Sulfur^(i)) 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Substances used: ^(a))NR TSR: natural rubber (TSR = technically specified rubber). ^(b))Europrene Neocis BR 40, from Polimeri. ^(c))S-SBR: Sprintan ® SLR-4601, from Trinseo. ^(d))Silica: ULTRASIL ® VN 3 GR from Evonik Industries AG (precipitated silica, BET surface area = 175 m²/g). ^(e))TDAE oil: TDAE = treated distillate aromatic extract. ^(f))6PPD: N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD). ^(g))DPG: N,N′-diphenylguanidine (DPG). ^(h))CBS: N-cyclohexyl-2-benzothiazolesulfenamide. ^(i))Sulfur: ground sulfur.

The mixture was produced by processes customary in the rubber industry in three stages in a laboratory mixer of capacity 300 millilitres to 3 litres, by first mixing, in the first mixing stage (base mixing stage), all the constituents apart from the vulcanization system (sulfur and vulcanization-influencing substances) at 145 to 165° C., target temperatures of 152 to 157° C., for 200 to 600 seconds. In the second stage, the mixture from stage 1 was thoroughly mixed once more, performing what is called a remill. Addition of the vulcanization system in the third stage (ready-mix stage) produced the finished mixture, with mixing at 90 to 120° C. for 180 to 300 seconds. All the mixtures were used to produce test specimens by vulcanization under pressure at 160° C.−170° C. after t954100 (measured on a moving disc rheometer to ASTM D 5289-12/ISO 6502).

The general process for producing rubber mixtures and vulcanizates thereof is described in “Rubber Technology Handbook”, W. Hofmann, Hanser Verlag 1994.

Rubber testing was effected in accordance with the test methods specified in Table 2. The results of the rubber testing are reported in Table 3.

TABLE 2 Physical testing Standard/conditions Viscoelastic properties of the RPA (“rubber process vulcanizate at 70° C., 1.0 Hz analyzer”) in accordance Payne effect of dynamic storage with ASTM D6601 from the modulus G′(1%)-(G′100%)/kPa second strain sweep Viscoelastic properties of the from dynamic-mechanical vulcanizate at 55° C. measurement according to Payne effect of dynamic storage DIN 53 513 measured in a modulus E′(0.15%)-E′ (8%)/MPa strain sweep at 0.15% and 8% elongation Rod tensile test at 23° C. to DIN 53 504 Fracture energy density/J/cm³ the fracture energy density corresponds to the work required before fracture, based on the volume of the sample

TABLE 3 Mixture Mixture Mixture Mixture 1 2 3 4 E′(0.15%)-E′(8.0%)/MPa 7.7 7.6 6.4 7.2 G′(1%)-G′(100%)/kPa 1089 1046 1096 1106 Fracture energy 25.0 23.6 26.7 23.4 density/J/cm³ Mixture Mixture Mixture Mixture Mixture 5 6 7 8 9 Inv. Inv. Inv. Inv. Inv. E′(0.15%)-E′(8.0%)/MPa 4.2 4.4 5.7 5.9 G′(1%)-G′(100%)/kPa 859 908 915 965 922 Fracture energy 29.7 32.6 31.8 27.6 39.9 density/J/cm³ Mixture Mixture Mixture Mixture Mixture 10 11 12 13 14 Inv. Inv. Inv. Inv. Inv. E′(0.15%)-E′(8.0%)/MPa 5.8 4.7 4.8 4.4 4.8 G′(1%)-G′(100%)/kPa 930 885 890 918 911 Fracture energy 33.9 39.1 37.0 38.9 39.6 density/J/cm³

Compared to the comparative mixtures, the inventive mixtures feature a reduced Payne effect, as apparent from the smaller differences for the dynamic storage modulus E′ from the Eplexor measurement and the dynamic stiffness G′ from the RPA measurement, which results in an improvement in hysteresis characteristics and reduced rolling resistance. Moreover, the silane mixtures according to the invention lead to advantages in bear properties as a result of an improved fracture energy density.

Example 29: Rubber tests

The formulation used for the rubber mixtures is specified in Table 4 below. The unit phr means parts by weight based on 100 parts of the raw rubber used. In the silane mixtures, some of the silane that reacts with the rubber during the vulcanization is replaced by the second silane which is unreactive toward the rubber.

TABLE 4 Mixture 20/ Mixture 21/ Mixture 22/ Mixture 23/ Mixture 24/ Mixture 25/ Mixture 26/ Mixture 15/ Mixture 16/ Mixture 17/ Mixture 18/ Mixture 19/ phr phr phr phr phr phr phr phr phr phr phr phr Inv. Inv. Inv. Inv. Inv. Inv. Inv. 1st stage NR^(a)) 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 BR^(b)) 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 S-SBR^(c)) 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 Silica^(d)) 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 TDAE oil^(e)) 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 6PPD^(f)) 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Antiozonant 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 wax Zinc oxide 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Stearic acid 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Comp. Ex. 14 8.83 Comp. Ex. 15 7.99 Comp. Ex. 16 7.16 Comp. Ex. 17 6.54 Comp. Ex. 18 6.39 Example 11 9.68 Example 12 8.85 Example 13 8.03 Example 14 7.20 Example 15 9.43 Example 16 8.66 Example 17 7.91 2nd stage Stage 1 batch 3rd stage Stage 2 batch DPG^(g)) 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 CBS^(h)) 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Sulfur^(i)) 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Mixture 27/ Mixture 28/ Mixture 29/ Mixture 30/ Mixture 31/ Mixture 32/ Mixture 33/ Mixture 34/ Mixture 35/ Mixture 36/ phr phr phr phr phr phr phr phr phr phr Inv. Inv. Inv. Inv. Inv. Inv. Inv. Inv. Inv. Inv. 1st stage NR^(a)) 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 BR^(b)) 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 S-SBR^(c)) 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 72.0 Silica^(d)) 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 TDAE oil^(e)) 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 6PPD^(f)) 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Antiozonant 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 wax Zinc oxide 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Stearic acid 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Example 18 10.42 Example 19 9.41 Example 20 8.40 Example 21 12.36 Example 22 10.86 Example 23 9.37 Example 24 7.87 Example 25 15.60 Example 26 13.29 Example 27 10.99 2nd stage Stage 1 batch 3rd stage Stage 2 batch DPG^(g)) 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 CBS^(h)) 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Sulfur^(i)) 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Substances used: ^(a))NR TSR: natural rubber (TSR = technically specified rubber). ^(b))Europrene Neocis BR 40, from Polimeri. ^(c))S-SBR: Sprintan ® SLR-4601, from Trinseo. ^(d))Silica: ULTRASIL ® VN 3 GR from Evonik Industries AG (precipitated silica, BET surface area = 175 m²/g). ^(e))TDAE oil: TDAE = treated distillate aromatic extract. ^(f))6PPD: N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD). ^(g))DPG: N,N′-diphenylguanidine (DPG). ^(h))CBS: N-cyclohexyl-2-benzothiazolesulfenamide. ^(i))Sulfur: ground sulfur.

The mixture was produced in processes customary in the rubber industry in three stages in a laboratory mixer of capacity 300 millilitres to 3 litres, by first mixing, in the first mixing stage (base mixing stage), all the constituents apart from the vulcanization system (sulfur and vulcanization-influencing substances) at 145 to 165° C., target temperatures of 152 to 157° C., for 200 to 600 seconds. In the second stage, the mixture from stage 1 was thoroughly mixed once more, performing what is called a remill. Addition of the vulcanization system in the third stage (ready-mix stage) produced the finished mixture, with mixing at 90 to 120° C. for 180 to 300 seconds. All the mixtures were used to produce test specimens by vulcanization under pressure at 160° C.−170° C. after t954100 (measured on a moving disc rheometer to ASTM D 5289-12/ISO 6502).

The general process for producing rubber mixtures and vulcanizates thereof is described in “Rubber Technology Handbook”, W. Hofmann, Hanser Verlag 1994.

Rubber testing was effected in accordance with the test method specified in Table 5. The results of the rubber testing are reported in Table 6.

TABLE 5 Physical testing Standard/conditions Viscoelastic properties of the RPA (“rubber process vulcanizate at 70° C., 1.0 Hz analyzer”) in accordance with ASTM D6601 from the second strain sweep (1%-100%) Loss factor tan δ at 10% strain

TABLE 6 Mixture Mixture Mixture Mixture Mixture 15 16 17 18 19 tan δ (10%) RPA 0.214 0.221 0.223 0.183 0.187 Mixture Mixture Mixture Mixture Mixture 20 21 22 23 24 Inv. Inv. Inv. Inv. Inv. tan δ (10%) RPA 0.152 0.152 0.149 0.172 0.160 Mixture Mixture Mixture Mixture Mixture 25 26 27 28 29 Inv. Inv. Inv. Inv. Inv. tan δ (10%) RPA 0.161 0.165 0.159 0.161 0.169 Mixture Mixture Mixture Mixture Mixture 30 31 32 33 34 Inv. Inv. Inv. Inv. Inv. tan δ (10%) RPA 0.159 0.155 0.166 0.177 0.150 Mixture Mixture 35 36 Inv. Inv. tan δ (10%) RPA 0.160 0.169

The partial exchange of the rubber-reactive silane for the second silane leads to improved rolling resistance (tan δ at 10% strain measured at 70° C.) in the mixtures according to the invention compared to the comparative mixtures. 

The invention claimed is:
 1. A silane mixture, comprising a silane of formula (I) (R¹)_(y)(R²)_(3-y)Si—R³—(S—R⁴)_(n)—S_(x)—R⁵  (I); and a silane of formula (II) (R¹)_(y)(R²)_(3-y)Si—R³—S—R³—Si(R¹)_(y)(R²)_(3-y)  (II), wherein R¹ is independently a C1-C10-alkoxy group, phenoxy group, C4-C10-cycloalkoxy group, or alkyl polyether group —O—(R⁶—O)_(r)—R⁷ where R⁶ being a divalent C1-C30 hydrocarbon group, r being an integer in a range of from 1 to 30, and R⁷ being a monovalent alkyl, alkenyl, aryl, or aralkyl group, R² is independently a C6-C20-aryl groups, C1-C10-alkyl groups, C2-C20-alkenyl groups, C7-C20-aralkyl group, or halogen, R³ is independently a divalent C1-C30 hydrocarbon group, R⁴ is independently a divalent C1-C30 hydrocarbon group, x is an integer in a range of from 1 to 10, wherein, when x is 1, R⁵ is a —C(═O)—R⁸ group with R⁸ being H, a C1-C20 alkyl group, C6-C20-aryl group, C2-C20-alkenyl group, or a C7-C20-aralkyl group and n is 0, 1, 2, or 3, wherein, when x is in a range of from 2 to 10, R⁵ is —(R⁴—S)_(n)—R³—Si(R¹)_(y)(R²)_(3-y) and n is 1, 2 or 3, and y is independently 1, 2, or 3, or wherein the silane of the formula (I) is (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S₂—(CH₂)₆—S—(CH₂)₃—Si(OEt)₃, (EtO)₃Si—(CH₂)—S—(CH₂)₆—S—C(═O)—CH₃, (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—C₇H₁₅, or (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S-—C(═O)—C₁₇H₃₅, and the silane of the formula (II) is (EtO)₃Si—(CH₂)₃—S—(CH₂)₃—Si(OEt)₃, and wherein a molar ratio of the silane of the formula (I) to the silane of the formula (II) is in a range of from 20:80 to 90:10.
 2. The mixture of claim 1, wherein n is
 1. 3. The mixture of claim 2, wherein the silane of the formula (I) is (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S₂—(CH₂)₃—Si(OEt)₃, (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—CH₃, (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—C₇H₁₅, or (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—C₁₇H₃₅, and wherein the silane of the formula (II) is (EtO)₃Si—(CH₂)₃—S—(CH₂)₃—Si(OEt)₃.
 4. The mixture of claim 1, wherein the molar ratio of the silane of the formula (I) to the silane of the formula (II) is in a range of from 35:65 to 90:10.
 5. A process for preparing the silane mixture of claim 1, the process comprising: mixing the silane of the formula (I) (R¹)_(y)(R²)_(3-y)Si—R³—(S—R⁴)_(n)—S_(x)—R⁵  (I), and a silane of the formula (II) (R¹)_(y)(R²)_(3-y)Si—R³—S—R³—Si(R¹)_(y)(R²)_(3-y)  (II), in a molar ratio in a range of from 15:85 to 90:10.
 6. The process of claim 5, wherein n is
 1. 7. The process of claim 5, wherein the molar ratio of the silane of the formula (I) to the silane of the formula (II) is in a range of from 35:65 to 90:10.
 8. The process of claim 5, wherein the silane of the formula (I) is (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S₂—(CH₂)₃—Si(OEt)₃, (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—CH₃, (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—C₇H₁₅, or (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—C₁₇H₃₅, and wherein the silane of the formula (II) is (EtO)₃Si—(CH₂)₃—S—(CH₂)₃—Si(OEt)₃.
 9. The mixture of claim 1, wherein R¹ in the silane of the formula (I) and (II) is independently a C1-C10-alkoxy group.
 10. The mixture of claim 1, wherein R¹ in the silane of the formula (I) and (II) is independently a phenoxy group.
 11. The mixture of claim 1, wherein R¹ in the silane of the formula (I) and (II) is independently a C4-C10-cycloalkoxy group.
 12. The mixture of claim 1, wherein R¹ in the silane of the formula (I) and (II) is independently an alkyl polyether group —O—(R⁶—O)_(r)—R⁷, wherein R⁷ is a monovalent alkyl, alkenyl, aryl, or aralkyl group.
 13. The mixture of claim 1, wherein R¹ in the silane of the formula (I) and (II) is independently an alkyl polyether group —O—(R⁶—O)_(r)—R⁷, and wherein R⁷ is a monovalent alkyl.
 14. The mixture of claim 1, wherein the silane of the formula (I) is (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S₂—(CH₂)₆—S—(CH₂)₃—Si(OEt)₃.
 15. The mixture of claim 1, wherein the silane of the formula (I) is (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—CH₃.
 16. The mixture of claim 1, wherein the silane of the formula (I) is (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—C₇H₁₅.
 17. The mixture of claim 1, wherein the silane of the formula (I) is (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—C₁₇H₃₅.
 18. The process of claim 5, wherein the silane of the formula (I) is (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S₂—(CH₂)₆—S—(CH₂)₃—Si(OEt)₃.
 19. The process of claim 5, wherein the silane of the formula (I) is (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—CH₃.
 20. The process of claim 5, wherein the silane of the formula (I) is (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—C₇H₁₅ or (EtO)₃Si—(CH₂)₃—S—(CH₂)₆—S—C(═O)—C₁₇H₃₅. 